1. Field of the Invention
This invention relates to the concurrent shaping and polishing of electrically-conductive materials. More specifically, the invention is method and system for deterministically shaping and polishing an electrically-conductive material by employing electrochemical and mechanical shaping/polishing at the same time.
2. Description of the Related Art
Optical component fabrication using metals or ceramic materials involves many grinding and/or machining plus polishing steps to achieve the proper form to the tolerances required by imaging or photonic focusing instruments. Conventional manufacturing methods require many days or even months of precise shaping and polishing to improve selected areas of the component. This improvement comes from precise measurements and, usually, manual operations to apply additional polishing to the measured discrepancy.
More modern methods used to overcome the extreme obstacles of manufacturing precise optics (e.g., those used in space exploration or short wavelength light imaging) include selective ion plasma etching and magnetorheological polishing with ferro-fluids in a magnetic field. While both techniques can be accomplished with computer control, the methods are extremely costly and equipment intensive.
Ion plasma etching requires placement of the optical component in a vacuum chamber, expensive radio-frequency amplifiers, and vacuum compatible controllers to selectively remove “high” areas from the component. In order to measure the work progress, the vacuum must be released and the re-established thereby increasing processing time. Magnetorheological polishing with ferro-fluids in a magnetic field is precise, but requires additional loading on the part thereby limiting the minimum stiffness of delicate lightweight optical components. Further, these two deterministic methods require capital investments of hundreds of thousands of dollars, special operator training, and special facilities considerations. In addition, the size and/or geometry of the components that can be processed is limited to the size/geometry of the equipment.
Another polishing process known as chemical mechanical polishing (CMP) is used to assist in the planarization of flat wafers. In this process, corrosive chemicals are mixed with polishing slurries to aid in substrate material removal by increasing the rate and in some cases improving the surface finish. The oxidation portion of the corrosion reaction is provided by an oxidizing substance such as hydrogen peroxide, nitric acid, perchloric acid, or ammonium persulfate, etc. Unfortunately, most of these oxidants are very hazardous. These processes are used with flat wafers, particularly silicon, for improved planarization. More recent processes have included electrochemical etching superimposed upon a chemical mechanical planarization process. However, no deterministic shaping is provided by these processes.